Mechanisms of developmental and reproductive toxicity from preconceptional BaP exposure The University of Mississippi ABSTRACT Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) that represents a class of ubiquitous environmental contaminants derived from the incomplete combustion of carbon. Human exposures to PAHs are associated with developmental and reproductive deficits. The goal of this R21 project is to characterize the transcriptomic and epigenetic changes associated with preconceptional exposure to BaP. Specifically, we will determine the role of the aryl hydrocarbon receptor (AhR) in BaP-induced multigenerational phenotypes. The AhR is a ligand activated transcription factor that is critical in regulation of diverse cellular functions from xenobiotic metabolism to cellular proliferation and differentiation. AhR activation is recognized in etiologies for birth defects and embryo lethality. Our central hypothesis is that persistent toxicity of BaP is dependent on the BaP-AhR interaction and AhR activation affects transcriptomic and DNA methylation profiles. To test this hypothesis, we will use zebrafish, an established model in developmental toxicology, particularly in developmental origins of adult health and disease (DOHaD) research. We have reported that multigenerational developmental impacts are present in F1 and F2 offspring after parental only BaP exposure. Our study design will involve dietary BaP exposures to either wild type or AhR null F0 parents and will allow us to measure the relationships between global gene expression and epigenetic changes in DNA methylation status in F0 and F1 germ cells and F1 embryos. Differentially expressed and methylated genes will be evaluated to explain the AhR- and BaP-mediated adverse outcomes in development and reproduction. Comparing AhR null and wild type constitutive gene expression and methylation status in germ cells and embryos could also reveal currently unknown roles of AhR in normal physiology. A cross-over mating protocol will reveal the sex-dependence in molecular and phenotypic endpoints. This research will address the significant knowledge gap that exists related to mechanisms underlying BaP?s latent toxicity following preconceptional exposure. The proposed comprehensive ?omics approach is consistent with the R21 exploratory, high-risk, high-reward funding mechanism. Importantly, this study will address the NIEHS emphasis areas of environmental epigenetics and developmental basis of adult disease; areas currently lacking appropriate consideration in risk assessment.